Demi Lovato (right) and her half sister Madison De La Garza

The 'X Factor' USA judge admits the biggest motivation for her checking into rehab in October 2010 to curb her drug and alcohol addictions, self-harm issues and bulimia was the fear of setting a bad example for her 11-year-old half-sister, Madison De La Garza.

The 21-year-old star recalled in her tell-all interview with Access Hollywood: "The last time that I had an intervention, it was my management, my entire team, manager, lawyers, everyone, and my parents coming into a room saying if you don't get sober - my mom specifically said, 'You know, we're going to move back to Texas and you're not going to be able to be around your little sister.' "

Demi's mother Dianna Hart, who has also battled an eating disorder, warned Demi she would cut her out of Madison's life forever if the singer didn't get her act together.

Dianna explained: "I had to set an example for Madison ... I had to protect her and [Demi] knew that. So when I said, 'I'm moving back to Texas,' she knew that I finally meant it that time, and that's when we all sat down with her and said, 'This is it, you have to make a change or we're all going our separate ways because if you don't want this career, we're not going to want it for you.' "

Demi credits Madison, who played Eva Longoria's on-screen daughter Juanita Solis on 'Desperate Housewives', for saving her life.

The 'Neon Lights' singer also opened up about her depression and self-harming in the interview, during which she confessed to her past cocaine problem.

She said: "There should be no taboo about it. I self-harmed, and [my mother] worried all the time. Sometimes when you're feeling so numb just by being depressed, you just want to feel."